Preformed sound control shapes

ABSTRACT

AN ASPHALT MASTIC COMPOSITION FOR USE AS A VIBRATION DAMPING MEDIUM COMPRISING: (A) AN ASPJALT; (B) SHAPERETAINING AGENTS; (C) A MINERAL FILLER; AND (D) A HEAT-RESISTANT FIBROUS MATERIAL. THE PRESENT INVENTION IS MOST ADVANTAGEOUS WHERE PREFORMED SHAPES OF IRREGULAR CONFIGURATIONS ARE REQUIRED.

United States Patent 3,808,164 PREFORMED SOUND CONTROL SHAPES James A.Gulino, Lockport, 11]., and William J. Woodring, Highland Park, N.J.,assignors to GAF Corporation, New York, NY. No Drawing. Filed Oct. 20,1971, Ser. No. 190,821 Int. Cl. C08f 45/52; C08g 51/52 US. Cl. 26028.5AS 4 Claims ABSTRACT OF THE DISCLOSURE An asphalt mastic composition foruse as a vibration damping medium comprising: (a) an asphalt; (b)shaperetaining agents; (c) a mineral filler; and (d) a heat-resistantfibrous material. The present invention is most advantageous wherepreformed shapes of irregular configurations are required.

The present invention relates to a composition of matter suitable foruse in the manufacture of a moldable shape capable of retaining acontour of the body onto which it will be used in order to reducevibration and sound transmission from such body.

Applicants, in researching the prior art, have found that two generaltypes of sound-control material have been used where automotiveapplications were involved.

The first is concerned with a flexible flat sheet of filled asphaltmastic having a density of about 1 lb. per square foot. This material istreated in a manner enabling it to be surfaced with a variety of paperfilm and/or felted or non-woven mats. Once applied to a metallicsurface, this particular asphaltic composition has been able to minimizevibration noises by damping and simultaneously reducing the transmissionof sound.

A second type or class of product that has been used as a dash liner orhead liner is composed of a non-woven felt or fibrous mat compressionmolded to a specific shape. In this particular instance, the end productfunctions as a sound absorbent material. This is quite different to thatof aforementioned asphaltic sheet product which serves to reduce noisegeneration and noise transmission from the surface to which it isattached.

The present invention is more concerned with the first class of product,namely, an asphaltic sheet product, rather than the latter product whichis outside of the scope of the present invention.

A modification of the fibrous product is found in US. Pat. 3,429,728.According to this reference, a sound-in sulating barrier is formed byimpregnation of a preformed fibrous mat with asphaltic material. Whilesuch product is good, it is costly and the fibrous mat is unnecessaryfor sound-damping characteristics.

While applicants have endeavored to evaluate and establish parameters onthe composition of matter used in the present invention, with particularemphasis on automotive applications, it is to be understood that thepresent invention is not intended to be so limited. It has also beenfound that the composition of matter has useful applications in mostevery area of manufacturing and endproduct usage where it is desired tocontrol vibration and sound transmission, such as in different types ofmetal cabinets.

A main object of the present invention is to provide a composition ofmatter not subject to one or more of the disadvantages attributable tothe prior art.

Another main object of the present invention is to provide a compositionof matter having improved sounddamping qualities.

Another object of the present invention is to provide a method ofutilization of a composition of matter for manufacturing preformedmolded shapes which require less fitting than the present type ofmaterials.

Still another object of the present invention is to provide acomposition of matter which has the ability to substantially retain itsshape after being formed into a molded form.

Still another object of the present invention is to provide aneasy-to-install, low-cost composition of matter which is moldable to apre-selected shape.

Other objects and advantages will be apparent from the followingdescription of the invention, particularly in the appended claims.

The attainment of the above objects is made possible by the provisionsof the present invention which include an asphalt mastic compositionsuitable for use as a vibration-damping medium comprising:

(a) an asphalt;

(b) shape-retaining agents;

(c) a mineral filler; and

(d) a heat-resistant fibrous material.

The present invention is the result of numerous empirical approaches tofinding an asphaltic composition that is capable of being produced in apreshaped manner to improve the ease of installation especially where acomplex shape is required and in so doing, applicants have endeavored toeliminate the heretofore necessary steps of cutting and fitting of flatmastic sheets and forms to obtain a reasonably close fit with the bodyonto which it is placed.

For an example, in a particular use, such as a rear wheelhouse cover (tobe found over the Wheel attached to the auto body) in the manufacture ofautomobiles, such mastic products were usually fitted by hand and had tobe slit and cut since the shape upon which the mastic was to be fit wasquite irregular.

Testing procedures utilizing the present composition indicated that thespecimen with the preformed mastic membrane provided sound levels twozones below the control level used with heretofore available fiat sheetmastic material. These tests were performed on two test automobiles andwere evaluated for sound and noise levels. The improved sound levelreduction resulted basically from the nearly perfect fit which yieldedimproved vibration damping characteristics of the molded product. Ofnoteworthy importance was the fact that there was substantialelimination of the necessary fitting and slitting function normallyrequired when using flat sheet mastic material.

The presently preformed shaped mastic material eliminates slits and cutsinto the spaces between part openings previously required for properfitting of the mastic material. Through such openings sound could havebeen transmitted to the surrounding areas.

The present invention, including the composition of matter, has aparticularly useful characteristic in automotive use in that it acts asa sound deadener and especially saves in direct labor costs duringinstallation of the particular part molded from the composition ofmatter of the present invention. In effect, there is provided anessentially perfect fit with resultant sound properties that arenoticeably favorable compared to the prior art. The positive fit andself-indexing characteristics, that is, the ability to immediately situpon the substrate base material to which it is being fitted reduces orsubstantially eliminates the problems usually associated with assemblyline operations, for an example, access or mounting holes which requirespecial alignment. The preformed mastic shape developed through the useof applicants composition maintains its shape after installation. Thischaracteristic is noteworthy when compared to prior art flat mastic,since the fiat material must be forced into position during the assemblyoperation and sometimes tends to return to its flat condition unless insome manner restrained.

Applicants have also employed a method of manufacturing a premoldedshape employing the inventive asphalt mastic composition including thesteps of: introducing said asphalt mastic into a female mold, coolingthe mastic composition at the surface of said mold, inverting androtating said mold by hand or mechanical means to pour off any excessfiuid mastic, circulating water or fluid through the mold to effectfurther cooling and permit easy withdrawal of the finished product fromthe mold, and then withdrawing the product from the mold.

According to the present invention, the composition of matter used tomold the preformed shape includes an asphalt, in amounts of about15-30%, preferably about 18-28%, mineral filler material,shape-retaining agents and fibrous materials for reinforcement. Theshape-retaining agents may include thermoplastic resins such aslow-density polyethylene, polyamides, polypropylene, polyvinyl acetate,polyvinyl chloride, ethylenevinyl acetate copolymers, in amounts rangingfrom about 3.0% to about 12%, preferably 5.0% to 7.0%; hydrocarbonresins such as styrene indene terpolymers and homologs thereof, alkyland alicyclic aliphatic hydrocarbons such as dichloropentadiene andhomologs thereof, and polymerization products of aliphatic C typediolefins and solidified hydrocarbons and natural occurring asphaltssuch as gilsonite in amounts ranging from about 1% to about 6%,preferably about 2 to about 4%; copolymers including piperylene andisoprene unsaturates and polymerization products of high-boilingaromatic fractions produced as a by-product from the thermal cracking ofpetroleum streams cut from crude oil such as naphthenic andanthracenic-containing polymers; any one or combination of which may beemployed in amounts ranging from about 3.0% to about 11.0% preferablyabout 5.0% to about 7.0%; also: indene or coumarone-indene resins andmonovinyl aromatic resins such as styrenated resins, polystyrene, vinylnaphthalenes and the like in amounts ranging from about 3.0% to about9.0% preferably about 5.0% to about 7.0%; also, natural or syntheticWaxes having the general formula RCONHR -NHCOR, wherein R=an alkyl oralkenyl having 12 to 1-8 carbon atoms and R =an alkylene group having 1to 6 carbon atoms, such as the ethylene bis(stearamide) and propylenebis(oleylamide), polyamide types and like waxes in amounts ranging fromabout 2.0% to about 7.0% preferably about 4.0% to about 6.0%. Many ofthe shaperetaining agents also function as viscosity control agentswhich is of importance during the molding operation.

Suitable filler materials have been found to include ground limestone,rock dust, clay, sand or other suitable mineral fines and the like inamounts ranging from about 60% to about 80% preferably about 65% to 75%.

The heat-resistant fibrous material may be chopped, shredded, etc.fiberglass, asbestos fiber or heat-resistant organic fibers such assulphate cellulosic fibers preferably bleached, and other fibers havinga basis of silicones or mineral-filled silicones and resins such asphenol-formaldehyde resins, polytrifluorochloroethylene resins,polytetrafluoroethylene resins, mixtures thereof and like resins inamounts ranging from about 0.5% to about 3.0%, preferably about 0.5% toabout 1.5%.

The size of the particles, rods, pellets or fibers can vary from about0.5 micron to about 20.0 microns.

All of the aforementioned materials when used in appropriate amounts andin correct combination with one another are basically formulated toprovide stiffness for shape-retention in conformance with apredetermined form, while at the same time, retaining a high degree ofviscoelastic behavior for the GQIIect vibration damping characteristic.

The following examples are shown for purposes of illustration andprovide a typical preferred formulation of the molded mastic compositionof matter as it is used in the present invention. All parts andproportions mentioned herein and in the claims are by weight unlessotherwise indicated.

EXAMPLE 1 Percent Asphalt ll85 F. softening point (S.P.) 20.0 Anon-reactive, non-saponifiable, thermoplastic petroleum hydrocarbonresin made from a highboiling aromatic petroleum fraction 6.0 a-Methylstyrene polymeric resin 1 240-255 F.

Limestone 71.0 Chopped fiberglass 0A") 1.0

1 A Friedel-Crafts catalyzed reaction product with a molecular weight ofless than 1500.

Example 1, the hydrocarbon resin and the polymeric u-methyl styrene, arebelieved to function as stifiening and shape-retaining components andthe limestone provides most of the mass of the overall material inproducing an end product that is capable of providing the sound-controlcharacteristics according to the present invention. The fiberglass isadded to impart the necessary tensile strength, tear-resistance and thelike.

EXAMPLE 2 Percent Asphalt 180-195 F. (S.P.) 20.0 A non-reactive,non-saponifiable, thermoplastic petroleum hydrocarbon resin made from ahigh- 1 A natural occurring asphalt.

In the above formulation, it will be noted that the wax component(Example 2) provides viscosity control and improved shape retention atelevated temperatures, while at the same time there may be some loss inthe ability to handle the end shape as is evidenced by a lower tensilestrength as compared to that of the first example. In this sameillustration, the actual molding of the preformed shape was carried outin the manner described previously.

The formulations given and shown in Examples 1, 2 and 3 include rangesfor the critical components. However, variations within the limitsindicated have been found not to materially affect the finished productperformance and the actual choice of formulation can be based upon thecomplexity of the specific parts being molded, the severity of handling,cost and use considerations and the like.

During the preparation of the composition of matter, normal mixingtechniques were employed, that is, asphalt was charged into a suitablemixer and maintained at a t mp rature of about 300 to 400 F. Thehydrocarbon resin and the styrene components were then added while thetemperature was maintained at the aforementioned level. Thereafter,limestone and fiberglass were added. Agitation of the mixture inaccordance with the techniques known in the art was maintainedthroughout the entire addition process to facilitate substantiallyuniform mixing of the entire composition.

Once the composition of matter is developed, thereafter, it is employedin a molding operation for conforming the composition to a preformedshape suitable for production use. In the foregoing example, the formingof the complex molded shape was used, for example, on a wheelhouse coverof an automobile. The process employed in the actual casting operationis one that is mentioned for illustrative purposes only. In thisparticular instance, a slush casting process was employed. A layer ofmastic at the inner mold surface cools sufiiciently to resist the flowof material. Thereafter, the mold is inverted through suitable means inorder to pour off the excess molten mastic material. Cooling of the moldto about 150 to about 100 F. takes place to allow the article beingformed to be removed from the mold. It has been found that the cycle forthe molding operation is in the neighborhood of about 30 to about 90seconds, the preferred time being about 60 seconds. Cooling of thepreformed shape may be accomplished by circulating water or other fluidat about 48 F. through the mold while the mastic temperature is about360 F. For purposes of evaluating the present invention, a number ofduplicate parts were molded in a like manner and tested for sound andshape-retention properties. The sound testing, as previously described,included providing a two-zone reduction in a test automobile whencompared over conventional mastic product which is usually available ina flat sheet and which has to be cut by an operator to a selected shape.The physical properties of the resultant products are depicted in Table1 below.

TABLE 1 Control I II III Caliper (in.) 0.125 0.120 0. 120 0.120 Tensilestrength (average) (Scott, 1bs./

nc width) 34 25 34 Stiffness (Tinius Olsen) 0.75# total load, 2" span,30 angle AMD 5 29 21 32 Direct reading, average WMD 6 37 27 46 Heatdistortion temp. F.) 1 1" sag across 2" span both ends supportecL- 170215 260 215 Heat deflection temp. F.) 1 1 sag across 2" span one endfree, one clamped 70 122 126 114 Impact resistance (inch-pounds) 1" x 1exposed, clamp one edge 0.5# weight dropped in center of exposed portion0. 75 3. 2. 0 3.

1 Rate of temperature rise for heat distortion and heat deflection testswas approximately 1 F. per minute.

When studying Table 1 above, it can be seen that the shape-retentioncharacteristics as measured under control heat test is quite superiorfor Examples 1 to 3 (see pages 10 and 11) as compared to a controlformulation. The control formulation is composed solely of asphalt andlimestone and is a standard formulation used commercially to producenon-molded sound control membranes.

This invention has been disclosed with respect to certain preferredembodiments, and it will be understood that modifications and variationsthereof will become obvious to persons skilled in the art and areintended to be included within the spirit and purview of thisapplication and the scope of the appended claims.

What is claimed is:

1. A vibration-damping mastic composition comprising approximately byweight:

(a) 15 to 30% of an asphalt having an S.P. of about (b) 1 to 6% ofgilsonite,

(c) 3 to 11% of a non-reactive, non-saponifiable thermoplastic petroleumhydrocarbon resin made from a high boiling aromatic petroleum fraction,

(d) 60 to of ground mineral fines, and

(e) 0.5 to 3% of chopped fiberglass or asbestos fiber.

2. A composition as defined in claim 1 wherein component (d) islimestone.

3. A composition as defined in claim 1 wherein component (e) isfiberglass.

4. A composition as defined in claim 1 comprising approximately byweight (a) 26.0% of an asphalt having an S.P. of about (b) 3.0% ofgilsonite,

(c) 3.0% of a non-reactive, non-saponifiable, thermoplastic petroleumhydrocarbon resin made from a high boiling aromatic petroleum fraction,

(d) 67.0% of limestone, and

(e) 1.0% of chopped fiberglass.

References Cited UNITED STATES PATENTS 3,418,402 12/1968 Grissom 1062823,615,803 10/1971 Draper 26028.5 AS 3,556,819 1/1971 Koons 26028.5 AS3,345,316 10/ 1967 Nielsen 26028.5 AS 3,312,157 4/1967 Coscia 26028.5 AS3,144,423 8/ 1964 Belak 26028.5 AS 2,688,005 8/1954 Clayton 260-285 ASOTHER REFERENCES A. H. Warth: The Chemistry and Technology of Waxes, 2ndedition, 1956, Reinhold Pub., pp. 484-485.

MORRIS LIEBMAN, Primary Examiner P. R. MICHL, Assistant Examiner US. Cl.X.R.

